scholarly journals Investigation of Tensile Creep Behavior for High-Density Polyethylene (HDPE) via Experiments and Mathematical Model

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6188
Author(s):  
Qiang Mao ◽  
Buyun Su ◽  
Ruiqiang Ma ◽  
Zhiqiang Li
Keyword(s):  
Creep Behavior ◽  
High Density Polyethylene ◽  
Strain Curve ◽  
Reference Value ◽  
High Density ◽  
Tensile Creep ◽  
Uniaxial Tensile ◽  
Form Model ◽  
Short Time ◽  
Parameter Values

Temperatures of −25 °C, +5 °C, and +35 °C were selected to study the creep behavior of high-density polyethylene (HDPE). The ultimate tensile strength of HDPE materials was obtained through uniaxial tensile experiments and the time–strain curves were obtained through creep experiments. When the loaded stress levels were lower than 60% of the ultimate strength, the specimens could maintain a longer time in the stable creep stage and were not prone to necking. In contrast, the specimens necked in a short time. Then, the time hardening form model was applied to simulate the time–strain curve and the parameter values were solved. The parameter values changed exponentially with the stresses, thereby expanding and transforming the time hardening model. The expanded model can easily and accurately predict creep behaviors of the initial and stable creep stages as well as the long-term deformations of HDPE materials. This study would provide a theoretical basis and reference value for engineering applications of HDPE.

Fabrication and characterization of microwave cured high-density polyethylene/carbon nanotube and polypropylene/carbon nanotube composites

2019 ◽  
Vol 53 (15) ◽  
pp. 2091-2104 ◽  
Author(s):  
Gaurav Arora ◽  
Himanshu Pathak ◽  
Sunny Zafar
Keyword(s):  
Carbon Nanotube ◽  
High Density Polyethylene ◽  
High Density ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nanotube Composites ◽  
Carbon Nanotube Composites ◽  
Scanning Electron

Carbon nanotubes have been used as reinforcements in polymers due to their high elasticity, flexibility, and thermal conductivity. In this study, pellets of high-density polyethylene +20 wt% carbon nanotube and polypropylene +20 wt% carbon nanotube were cured using microwave energy. X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, uniaxial tensile test, and scanning electron microscopy was used to study morphology, thermal stability, and mechanical performance of the microwave-cured composites. X-ray diffraction analysis confirmed the bonding between the polymer and carbon nanotube as the peaks shifted and intensified. From the thermal study, it was observed that melting point of the composites is affected by microwave curing and the crystallinity of high-density polyethylene/carbon nanotube and polypropylene/carbon nanotube changed by 57.67% and 47.28%, respectively. Results of the uniaxial tensile test indicated that Young’s modulus of microwave cured high-density polyethylene/carbon nanotube and polypropylene/carbon nanotube composites were improved by 295% and 787.8%, respectively. Scanning electron microscopic fractography shows the stretching of polymer over-lapped on carbon nanotubes in the direction of the applied load.

High-density polyethylene/cycloolefin copolymer blends, part 2: Nonlinear tensile creep

2006 ◽  
Vol 46 (10) ◽  
pp. 1363-1373 ◽  
Author(s):  
Jan Kolařík ◽  
Alessandro Pegoretti ◽  
Luca Fambri ◽  
Amabile Penati
Keyword(s):  
High Density Polyethylene ◽  
High Density ◽  
Tensile Creep ◽  
Copolymer Blends

Tensile Creep Behavior of HPC at Early Ages under Different Curing Temperatures

2011 ◽  
Vol 250-253 ◽  
pp. 434-439 ◽  
Author(s):  
Yang Yang ◽  
Peng Li ◽  
Yan Ping Wu
Keyword(s):  
Creep Rate ◽  
Creep Behavior ◽  
Strength Class ◽  
Concrete Specimen ◽  
Curing Temperature ◽  
Tensile Creep ◽  
Uniaxial Tensile ◽  
Creep Coefficient ◽  
The Difference ◽  
Uniaxial Tensile Creep

This paper presents an experimental investigation on tensile basic creep behavior of HPC at early ages by using a uniaxial tensile creep testing apparatus. Concrete specimens of 100×100×400mm with compressive strength class 60MPa was used, sealed and loaded at different curing temperature. The effects of the curing temperature and the age at loading on creep behavior are discussed. The results show that tensile specific creep and creep rate of HPC at early ages were governed by the age at loading. The specific creep, creep coefficient and creep rate were larger at earlier loading ages, and decreased exponentially with age at loading. The tensile specific creep decreased with curing temperature, but the difference in creep due to different curing temperatures decreased with the age at loading, and could be ignored while concrete specimen being loaded after the age of 7 days.

scholarly journals Flexural Creep Behavior of High-Density Polyethylene Lumber and Wood Plastic Composite Lumber Made from Thermally Modified Wood

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 262 ◽  
Author(s):  
Murtada Abass A. Alrubaie ◽  
Roberto A. Lopez-Anido ◽  
Douglas J. Gardner
Keyword(s):  
Creep Behavior ◽  
Creep Deformation ◽  
High Density Polyethylene ◽  
Creep Compliance ◽  
High Density ◽  
Wood Plastic Composite ◽  
Creep Stress ◽  
Plastic Composite ◽  
Thermally Modified Wood ◽  
Modified Wood

The use of wood plastic composite lumber as a structural member material in marine applications is challenging due to the tendency of wood plastic composites (WPCs) to creep and absorb water. A novel patent-pending WPC formulation that combines a thermally modified wood flour (as a cellulosic material) and a high strength styrenic copolymer (high impact polystyrene and styrene maleic anhydride) have been developed with advantageous viscoelastic properties (low initial creep compliance and creep rate) compared with the conventional WPCs. In this study, the creep behavior of the WPC and high-density polyethylene (HDPE) lumber in flexure was characterized and compared. Three sample groupings of WPC and HDPE lumber were subjected to three levels of creep stress; 7.5, 15, and 30% of the ultimate flexural strength (Fb) for a duration of 180 days. Because of the relatively low initial creep compliance of the WPC specimens (five times less) compared with the initial creep compliance of HDPE specimens, the creep deformation of HDPE specimens was six times higher than the creep deformation of WPC specimens at the 30% creep stress level. A Power Law model predicted that the strain (3%) to failure in the HDPE lumber would occur in 1.5 years at 30% Fb flexural stress while the predicted strain (1%) failure for the WPC lumber would occur in 150 years. The findings of this study suggest using the WPC lumber in structural application to replace the HDPE lumber in flexure attributable to the low time-dependent deformation when the applied stress value is withing the linear region of the stress-strain relationship.

Viscoelastic Finite Element Modeling of Bimodal High Density Polyethylene (HDPE) Piping Materials for Nuclear Safety-Related Applications

2010 ◽  
Author(s):  
Do-Jun Shim ◽  
Prabhat Krishnaswamy ◽  
Yunior Hioe ◽  
Sureshkumar Kalyanam
Keyword(s):  
Finite Element ◽  
Service Life ◽  
High Density Polyethylene ◽  
Viscoelastic Behavior ◽  
Time Dependent ◽  
Tensile Creep ◽  
Uniaxial Tensile ◽  
Fe Model ◽  
Creep Tests ◽  
Uniaxial Tensile Creep

The U.S. Nuclear Regulatory Commission (USNRC) has recently approved Relief Requests for the use of high density polyethylene (HDPE) piping in safety-related applications. The ASME Boiler and Pressure Vessel Code, meanwhile, has developed Code Case N-755 that defines the design and service life requirements for PE piping in nuclear plants though it has not as yet been approved by the USNRC. One of the issues of concern is premature failure of PE piping due to slow crack growth (SCG) that can initiate due to a combination of sustained loads, elevated temperatures, and a pre-existing defect. Understanding and predicting the SCG behavior is an essential step in developing a methodology for predicting the service life of PE piping. The first step in studying the failure process in a polymer under a constant sustained load is the selection of a suitable constitutive model to represent the time-dependent behavior of the material. In this paper, uniaxial tensile creep tests were performed for a bimodal HDPE (PE4710) piping material. This creep data was used to determine the viscoelastic material constants for this bimodal HDPE using a power-law creep model. These material constants were used in finite element (FE) analyses to study the viscoelastic behavior of the bimodal HDPE. As a first step, the FE model was verified by comparing the results from numerical simulations and experiments for a set of uniaxial tensile creep tests. The FE model was then applied to study the viscoelastic behavior of a SCG specimen. The time dependent stress and strain fields were investigated.

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